Liblouis User's and Programmer's Manual

2.6.3 Note about fallback behavior ¶

Contrary to older versions of liblouis there is limited fallback behavior. Generally opcodes have a very specific purpose. This is done for the sake of simplicity. While it would be possible to support more combinations of rules, Liblouis chooses to signal an error when certain combinations of opcodes are used (or not used).

For example, when a begemphphrase rule is defined it is required that there is also an endemphphrase definition. begemph must be combined with endemph. A begemphphrase rule is only allowed if there is also a begemphword. begemph and begemphword are mutually exclusive. Etc.

When new requirements for indicating emphasis arise that are not supported yet, either more opcode combinations might be enabled, or more specific opcodes might be added.